Abstract: This paper presents a new stochastic and heuristic searching algorithm,ant colony algorithm(ACA),and its applicanon to reserwir optimal operation.The main purpose of this paper is to investigate the applicability of ACA in solving "dimension difficulty" in the reserwir optimal operation problem.In the ACA,a set of co-operation ants work together to find a good solution to the reserwir optimal operation problem.The state transition rule,the global pherormne-updating rule and the neighbor search are also introduced to ensure the optimal solution.Once all the ants have completed their tours,a global pheromone-updating rule is then applied and the process is iterated until the stop condition is satisfied.A case study for solving "dimension difficulty" is presented in this paper.In contrast wrath the dynamic programming,the new algorithm shows its advantages on computing speed and convergence.